Do NOT use your best bottle of red wine for this recipe. Because you are changing the flavor of the wine, any good, cheap bottle of red wine will do!
Place the mulling spices in the muslin bag and simmer in water for 20-30 minutes. This will reconstitue the spices. Discard the water, add the bottle of red wine (retaining the spices) and warm. The spices will flavor the wine in about 15 minutes. You do not want to boil the mixture, as this will cook out the alcohol.